std::expected<T,E>::operator->, std::expected<T,E>::operator*
From cppreference.com
Primary template |
||
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constexpr
const T* operator-
>
(
)
const
noexcept
;
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(1) | (since C++23) |
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constexpr T* operator-
>
(
)
noexcept
;
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(2) | (since C++23) |
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constexpr
const T& operator*
(
)
const
&
noexcept
;
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(3) | (since C++23) |
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constexpr T& operator*
(
)
&
noexcept
;
|
(4) | (since C++23) |
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constexpr
const T&& operator*
(
)
const
&&
noexcept
;
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(5) | (since C++23) |
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constexpr T&& operator*
(
)
&&
noexcept
;
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(6) | (since C++23) |
void partial specialization |
||
|
constexpr
void operator*
(
)
const
noexcept
;
|
(7) | (since C++23) |
Accesses the expected value contained in *this.
1,2) Returns a pointer to the expected value.
3-6) Returns a reference to the expected value.
7) Returns nothing.
If has_value() is false, the behavior is undefined.
Return value
1,2)
std::addressof(
val
)
3,4)
val
5,6)
std::
move
(
val
)
Notes
These operators do not check whether the optional represents an expected value! You can do so manually by using has_value() or simply operator bool(). Alternatively, if checked access is needed, value() or value_or()
Example
Run this code
#include <cassert> #include <expected> #include <iomanip> #include <iostream> #include <string> int main() { using namespace std::string_literals; std::expected<int, std::string> ex1 = 6; assert(*ex1 == 6); *ex1 = 9; assert(*ex1 == 9); // *ex1 = "error"s; // error, ex1 contains an expected value of type int ex1 = std::unexpected("error"s); // *ex1 = 13; // UB, ex1 contains an unexpected value assert(ex1.value_or(42) == 42); std::expected<std::string, bool> ex2 = "Moon"s; std::cout << "ex2: " << std::quoted(*ex2) << ", size: " << ex2->size() << '\n'; // You can "take" the expected value by calling operator* on an std::expected rvalue auto taken = *std::move(ex2); std::cout << "taken " << std::quoted(taken) << "\n" "ex2: " << std::quoted(*ex2) << ", size: " << ex2->size() << '\n'; }
Possible output:
ex2: "Moon", size: 4 taken "Moon" ex2: "", size: 0
See also
| returns the expected value (public member function) |
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| returns the expected value if present, another value otherwise (public member function) |
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| checks whether the object contains an expected value (public member function) |
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| returns the unexpected value (public member function) |